Which women are at an increased risk of operative birth in the UK?

Introduction

In the UK, as in many other developed countries there has been a dramatic rise in the caesarean section rate, with no associated decrease in the number of instrumental births. Women who experience an operative birth are at an increased risk of adverse health outcomes, and poorer psychosocial wellbeing. Furthermore, operative births represent a substantial cost to the NHS.

Little is known about the maternal and fetal factors related to different modes of birth. This thesis explores these risk factors in a large contemporary population-based UK data source.

Aims

To explore the maternal and fetal risk factors for operative birth (including instrumental vaginal, emergency caesarean section and planned caesarean section) in a large UK sample.

Methods

The sample comprised 18,239 natural mother-infant pairs in the first wave of the Millennium Cohort Study, 2000-2002. Multivariable regression models were used to establish the independent socio-demographic, socio-economic, interpersonal, pregnancy and fetal predictors of mode of birth, stratified by parity where possible.

Findings

Women who were older, of some minority ethnic groups, non-UK born and of lower socio-economic status were generally at a higher risk of operative birth. Women of shorter stature, who experienced complications in pregnancy and who were obese pre-pregnancy were also at greater risk in most cases. Complications during labour, particularly malpresentation and fetal distress greatly increased the likelihood of operative birth. Finally, women who had infants with a gestational age or birth weight outside the normal range were at a higher risk of an unplanned operative birth, as were multiparous women with a male infant.

Discussion

Many characteristics of women and their infants independently predict the mode of birth they experience. Further research is needed to establish to what extent differences in mode of birth are a reflection of women‟s behaviours or health professional practice, and are therefore potentially modifiable.